WifiManager: add LocalOnlyHotspotObserverProxy

Add the proxy for LOHS observer callbacks to make sure we give updates
to calling apps on the correct thread.

This will be used in a follow-on CL.

Bug: 36704763
Test: mmma -j64 frameworks/base/
Change-Id: I20faa73325116426f45d9d8fabc45b279bd5a286
1 file changed